1. Field of the Invention
The present invention relates to an exchange and an exchange system in a communication network which is formed by a plurality of networks connected in series and each having different level diagram of a call signal (i.e., electrical level). In this case, a plurality of exchanges are provided at each end of the network, and the exchange system is formed by a plurality of relay lines each provided between exchanges.
2. Description of the Related Art
In a communication industry providing various services through public networks or private lines, there are many telephone companies that compete with each other on various services, for example, service of cost, quality of a call to be transmitted, and the like. In general, each telephone company has a private network which is adapted to its business strategy.
Further, almost companies have at least one branch exchange having high performance, and each company has private lines employing a compressed-coding transmission method between private branch exchanges, in order to save communication cost between a main office and a remote branch and to avoid many non-completed calls caused by busy state of the public network.
As a general structure, a private line is provided between private branch exchanges each of which is connected to the public network. Further, the public network is connected to a plurality of subscribers, and the other private branch exchange is connected to a plurality of extension lines within the company.
In this structure, an adjustment of the level of the call signal between the public network and the private line, or between exchanges is very important for realizing desirable high quality of the call. Particularly, in a long distance communication, there are many lines and exchanges between a sending side and a receiving side so that the quality of the call becomes worse. Accordingly, it is necessary to always improve the quality of calls in order to provide good service to the subscribers.
The primary object of the present invention is to provide an exchange enabling a high quality of calls.
Another object of the present invention is to provide an exchange system using the above exchanges enabling a high quality of calls.
Still another object of the present invention is to provide an exchange and an exchange system which can easily correct a very large or a very small level of the call signal to the normal level during a call.
In accordance with one aspect of the present invention, in an exchange including:
a call processing unit for processing a call from any one of plural subscriber lines, a main line, or a private line, selecting a communication route, identifying a completed call, and determining a call route to be used for transmitting a call signal;
a switch unit for establishing the call route determined by the call processing unit; and
a plurality of trunks for separately connecting to any one of plural subscriber lines, a main line, or a private line, interfacing with the call route for the call signal, and having a matching between the call processing and a predetermined signal method used in any one of the plural subscriber lines, a main line, or a private line; wherein the exchange comprises:
a single or plural decision units for determining whether an audio frequency signal which separately indicates a state of change of level of the call signal, is received or not, in the route formed by all or any one of the plural subscriber lines, a main line, or a private line; and
a single or plural variable units separately provided between each of the routes and a corresponding port of the switch, and performing the change of the level based on the state indicated by the audio frequency signal which gives a result of a decision by the decision unit, for the level of the call signal transmitted toward the route in which the result of the decision is true.
In accordance with another aspect of the present invention, in the same exchange as above: wherein the exchange comprises:
a single or plural decision units for determining whether an audio frequency signal which indicates a state of change of level of the call signal, is received or not, through the call route formed by the switch, in the route formed by all or any one of the plural subscriber lines, a main line, or a private line; and
a single or plural variable units separately provided between each of opposite routes, which corresponds to the selected route based on selection of the route, and a corresponding port of the switch, and performing the change of the level based on the state indicated by the audio frequency signal which gives a result of a decision by the decision unit, for the level of the call signal transmitted toward the route in which the result of the decision is true.
In accordance with still another aspect of the present invention, in the same exchange as above: wherein the exchange comprises:
a single or plural decision units for determining whether a line signal which separately indicates a state of change of level of the call signal, is received or not, in the route formed by all or any one plural subscriber lines, a main line, or a private line; and
a single or plural variable units separately provided between each of routes and a corresponding port of the switch, and performing the change of the level based on the state indicated by the line signal which gives a result of decision by the decision unit, for the level of the call signal transmitted toward the route in which the result of the decision is true.
In accordance with still another aspect of the present invention, in the same exchange as above: wherein the exchange comprises:
a single or plural decision units for determining whether an audio frequency signal which separately indicates a state of change of level of the call signal, is received or not, in the route formed by all or any one of plural subscriber lines, a main line, or a private line; and
a single or plural variable units separately provided between each of opposite routes, which corresponds to the selected route based on selection of the route, and a corresponding port of the switch, and performing the change of the level based on a predetermined state, for the level of the call signal transmitted toward the route through the port;
wherein the call processing unit further includes a unit for giving the state to the variable means corresponding to the opposite route based on selection of the route, within a single or plural variable units, when the result of decision performed by a single or plural variable units is true.
In accordance with still another aspect of the present invention, in the same exchange as above: wherein the exchange comprises:.
a single or plural decision units for determining whether a line signal which separately indicates a state of change of level of the call signal, is received or not, in the route formed by all or any one of plural subscriber lines, a main line, or a private line, converting the line signal to the audio frequency signal, and transmitting the converted audio frequency signal to the call route; and
a single or plural variable units separately provided between each of opposite routes, which can correspond to all routes based on selection of the route, and a corresponding port of the switch, and performing the change of the level based on a state indicated by the audio frequency signal, for the level of the call signal transmitted toward the route through the port.
In accordance with still another aspect of the present invention, in the same exchange as above: wherein the exchange comprises:
a single or plural decision units for determining whether a line signal which separately indicates a state of change of level of the call signal, is received or not, in the route formed by all or any one of plural subscriber lines, a main line, or a private line; and
a single or plural variable units separately provided between each of opposite routes, which can correspond to all routes based on selection of the route, and a corresponding port of the switch, and performing the change of the level based on a predetermined state, for the level of the call signal transmitted toward the route formed by the switch;
wherein the call processing means further includes means for giving the result of decision, which is performed by the decision means, and the state to the variable means corresponding to the opposite route based on selection of the route, within a single or plural variable means.
In a preferred embodiment, the exchange further comprises a single or plural detecting units provided separately corresponding to the opposite route which can correspond to all routes through the call route based on selection of the route, and performing whether the audio frequency signal is received or not through the call route formed by the switch and the trunk connected to each route;
wherein a single or plural variable units further comprises a unit for limiting the change when the result of decision performed by the detecting unit which is provided to the opposite route based on selection of the route, within a single or plural detecting units.
In another preferred embodiment, the exchange further comprises a single or plural detecting units provided separately corresponding to the route, and performing whether the audio frequency signal is received or not through the route;
wherein a single or plural variable units further comprises a unit for limiting the change when the result of decision performed by the detecting unit which is provided to the route corresponding to the opposite route having the variable unit, under selection of the route, within a single or plural detecting units.
In accordance with still another aspect of the present invention, there is provided an exchange system including the above exchange and comprising:
the above exchange being used as a first exchange; and
a second exchange connected to the first exchange through a relay line which corresponds to the main line or the private line, and exchanging the call on the relay line used as an incoming route or an outcoming route;
wherein the second exchange further comprises a signal conversion unit for indicating the state of the change for the level of the call signal to be transmitted toward any one of the subscriber lines, the main-line, or the private line, connected to its own exchange, supervising the line signal transmitted from any one of the subscriber lines, the main line, or the private line, converting the line signal to the audio frequency signal and transmitting the audio frequency signal to the relay line.